1. Field of the Invention
The present invention relates to a display device, in particular a display device having a non-rectangular display area.
2. Description of Related Art
In recent years, various types of devices equipped with a display device have become widespread. As better design and fashion suited to user's taste have been desired in these devices, the shapes of the devices have changed to satisfy such desires.
To cope with such a trend, some contrivance is sometimes made on the display area of such display devices. Although the display area usually has a rectangular shape, display areas having non-rectangular shapes such as circular and oval shapes have been also known.
In a display device, pixels are typically arranged in a matrix. Therefore, in a display device having a circular or oval shaped display area or the like, pixels located in the boundary portion of the display area are shielded in a circular arc shape. In such a case, since pixels having respective colors contained in one picture element are shielded in such a manner that their aperture ratios become unbalanced, the color balance of picture elements located on the edge of the display area becomes disrupted. In this way, color shift occurs on the edge of the display area, and thus deteriorating the display quality.
Several techniques have been disclosed in an attempt to solve the above-mentioned problem. FIG. 7 is a top view schematically illustrating a structure of an edge portion of the display area of a liquid crystal display device in accordance with related art 1 disclosed in Japanese Unexamined Patent Publication Application No. 2006-276580. In FIG. 7, an edge portion in the vicinity of the upper-right portion of an oval-shaped display area 1 is shown. Therefore, in FIG. 7, the display area 1 is shown on the lower-left side of the display-area edge 3, and a frame area 2 is shown on the upper-right side of the edge 3. In the related art 1, the line width of the black matrix on the color filter substrate is adjusted, as shown in FIG. 7, so that in a picture element 5 in which the pixels shielded by the frame area 2 are located, the aperture ratios of the pixels having respective colors become even. In this way, the color balance within a picture element 5, in which the pixel aperture ratios of the effective display areas 4R, 4G and 4B having respective colors are uneven since it contains pixels shielded by the frame area 2, becomes stable. Therefore, the occurrence of color shift on the display-area edge 3 can be prevented.
Meanwhile, FIG. 8 is a top view schematically illustrating a structure of an edge portion of the display area of a liquid crystal display device in accordance with related art 2. As in the case of FIG. 7, an edge portion in the vicinity of the upper-right portion of an oval-shaped display area 1 is shown in FIG. 8. Therefore, in FIG. 8, the display area 1 is shown on the lower-left side of the display-area edge 3, and a frame area 2 is shown on the upper-right side of the edge 3. In the related art 2, the pixels contained in all the picture elements 5, in which at least one pixel is shielded by the frame area 2, are turned off as shown in FIG. 8. In this way, picture elements 5, in which the pixel aperture ratios of the effective display areas 4R, 4G and 4B having respective colors are uneven since it contains pixels shielded by the frame area 2, are not displayed. Therefore, the occurrence of color shift on the display-area edge 3 can be prevented.
However, in the related art 1, the positions of the center lines 6, each of which is defined as a line vertically dividing the effective display area 4 into two parts having the same size, are different among picture elements adjacent to one another in the lateral direction of FIG. 7 depending on the level at which they are shielded by the frame area 2. Therefore, when a laterally straight line is displayed, the line does not become straight but becomes curved at the edge portion of the display area 1. Meanwhile, in the related art 2, the center lines 6 of the picture elements 5 arranged in the lateral direction become straight. Therefore, when a laterally straight line is displayed, the line is not curved at the edge portion of the display area 1. However, since the picture elements 5 in which at least one pixel is shielded by the frame area 2 are all turned off, it is impossible to form the outside shape of the display area 1 in a smooth oval or circular shape.
The present invention has been made to solve the above-mentioned problems, and an exemplary object of the present invention is to provide, in display devices having display areas having non-rectangular shapes such as circular and oval shapes, a display device having a display area with a smooth outside shape and an excellent display quality.